If Rusin's argument gets any more compelling over the next two weeks, Sveum might not have much of a choice.

Rusin pitched seven effective innings in a 3-1 loss to the Pittsburgh Pirates on Thursday night, allowing two runs and four hits while striking out two. He extended a string of stellar outings sure to leave a good impression with his manager heading into the winter.

"We'll cross those bridges when we get to it," Sveum said. "He's definitely put himself in a position to have every opportunity to make the rotation."

Facing one of the National League's best teams against lefties, Rusin (2-4) had his only hiccup in the fourth when he allowed consecutive RBI singles to Marlon Byrd and Pedro Alvarez. Otherwise, the lefty was lights out as he continued his steady rise through the ranks.

"When you pitch with confidence like he did today — he made his pitches — that's what you're going to get," Cubs catcher Welington Castillo said.

Rusin needed to be sharp on a night when Pirates All-Star Jeff Locke returned to his first-half form. Locke (10-5) gave up three hits over seven innings in his first victory in nearly two months, helping the Pirates win their fourth straight to tie St. Louis for the NL Central lead.

Mark Melancon worked out of a two-on, none-out jam in the ninth for his 14th save. Jordy Mercer went 2 for 4 with an RBI double in the eighth that provided an insurance run.

Locke was an All-Star in July but hadn't won since beating Cincinnati on July 21. He struggled through August and never worked more than 5 2-3 innings in any start as his ERA rose from 2.11 to 3.23.

The left-hander stressed he wasn't fatigued and appeared to find something last week against St. Louis, giving up just two earned runs while battling through five innings. He carried it forward against the Cubs, who were coming off an impressive series win against the Reds.

"He was able to stabilize himself last time out, find some rhythm, find some confidence," Pittsburgh manager Clint Hurdle said. "He had confidence, but some tangible confidence after a good solid outing."

Working both sides of the plate crisply — a hallmark of his stellar first half — Locke ran into only minor trouble against the Cubs. Darnell McDonald hit a ground-rule double to lead off the third and later scored on an RBI single by Starlin Castro.

That was all the Cubs could manage against Locke, who retired his final 10 batters thanks to more than a little help from his defense.

First baseman Justin Morneau scrambled into shallow right field in the fourth to make a snow-cone catch on McDonald's looper. Mercer made a spectacular jump throw from deep shortstop to nip Donnie Murphy in the sixth, and Gold Glove center fielder Andrew McCutchen slid on his belly to corral Junior Lake's sinking liner in the seventh.

"I already told 'Cutch that as a pitcher you see a lot of balls go over your head and you see him and you say there's no way he can close that gap," Locke said. "Before you know it, he's belly-up with the ball in his glove. Unbelievable play."

They were the kind of plays Locke wasn't getting during his six-week swoon. They are the kind he'll have to rely on if the Pirates want to emerge from a three-way battle with St. Louis and Cincinnati with their first NL Central title.

Pittsburgh clinched its first winning season in 21 years during an exhausting nine-game road trip that concluded Wednesday with a three-game sweep of Texas.

The Pirates were given a long ovation when they walked onto the field, as a crowded PNC Park in mid-September — a rarity over the last two decades — let a generation of frustration out in 30 seconds of pure joy.

"It was pretty impressive to get a standing ovation like that just to hit the 82 mark," Mercer said. "We've still got a lot of work left to do. There's unfinished business."

NOTES: The Cubs have switched to a six-man rotation for the final two-plus weeks of the season to give RHP Scott Baker more work. Baker is recovering from reconstructive elbow surgery. ... The series continues Friday when Charlie Morton (7-4, 3.44 ERA) faces Chicago's Jake Arrieta (2-2, 4.28).